A single bald eagle found dead in southern Delaware last Saturday didn't raise red flags for state wildlife officials.

But then a few hours later and a mile away, a startling scene unfolded: Eight bald eagles — distressed and disoriented — were discovered on the ground, barely moving on a fallow farm field.

"Seeing one in a field wouldn’t be irregular, but then so many of them — and they weren't sitting up," said Sgt. John McDerby of Delaware's Fish and Wildlife Natural Resources Police. "It was a devastating sight."

Three of the eagles died, two were rescued and the rest flew away, officials said. The following day, another dead bird was found during a sweep.

One of five eagles found in the Dagsboro, Delaware, area on March 19, 2016.DNREC Division of Fish &amp; Wildlife Natural Resources Police

The cluster of deaths comes just a month after 13 bald eagles died about 35 miles away on the Eastern Shore of Maryland — the largest single die-off of bald eagles in the state in three decades.

This mystery surrounding the bird species that has soared back from the brink of extinction has investigators and wildlife advocates asking: Is someone poisoning or intentionally harming these national symbols?

At this point, investigators can't say, but they aren't ruling out a criminal act.

In Maryland, necropsies indicated the birds did not die from natural causes, meaning diseases such as avian influenza can be ruled out. But they did not pinpoint a cause of death.

McDerby said test results of the eagle carcasses in Delaware could be made available early this week. In the meantime, he added, there is no evidence of a serial eagle killer on the prowl or any direct connection between the Delaware and Maryland cases.

The two birds rescued by the nonprofit Tri-State Bird Rescue of Newark, Delaware, are still under the group's care. Staff declined to provide information about their recovery because the investigation is ongoing, but said that if the creatures fully recuperate, they'll be released into the wild.

Edgell said he's not sure what took down the eagles on his land in Maryland. He found no evidence of tracks, after first thinking someone may have dumped the recognizable white-headed birds of prey on purpose.

He also saw no indications they had been shot or had other signs of trauma.

"I was dumbfounded, shocked and everything else," Edgell said. "I had never seen that many at one time, especially on my property."

Anyone convicted of causing the death of the federally protected bald eagle could be fined as much as $100,000 and sentenced to up to a year in prison.

The deaths come as bald eagles have made an impressive resurgence in the past five decades. They were nearly killed off after losing habitat and being threatened by the pesticide DDT. Federal protection status as an endangered species in 1967, however, helped to ensure their survival.

Even into the 1970s, bald eagles were shot fairly regularly, said Kevin McGowan, an ornithologist at the Cornell University Lab of Ornithology.

"The decrease in shooting was part of the reason the eagles have recovered so spectacularly (but just one part)," McGowan said in an email. "Populations are probably at a 100-year high. Growth of the eastern population over the last 20 years alone has been impressive."

Nationwide, the birds went from fewer than 500 breeding pairs in the Lower 48 in 1963 to over 11,000 pairs in 2007, when they were taken off the endangered species list, federal figures show.

Now, bald eagles — beloved as a national symbol of the United States — are celebrated. A pair of babies born at the National Arboretum in Washington, D.C., took the Internet by storm this month thanks to a live cam.

But the sudden loss of so many under strange circumstances should serve as a warning that the magnificent birds still need protection, experts say.